1. Field of the Invention
The present invention relates to an image pickup unit including a moving lens drive unit that drives a moving lens forward and backward, and an endoscope.
2. Description of the Related Art
Endoscopes provided with image pickup units for picking up optical images are used in, for example, a medical or industrial field. Such an endoscope can be introduced into a living body and a structure from the outside to the inside observe points that are hard to observe in the living body and the structure.
An image pickup unit of an endoscope is provided with an objective lens that forms an object image, and a typical image pickup device, for example, a CCD (charge-coupled device) or a CMOS (complementary metal oxide semiconductor) sensor disposed on an image forming surface of the objective lens.
For example, Japanese Patent Application Laid-Open Publication No. 2010-243195 discloses an endoscope that includes a moving lens holding barrel provided with a moving lens. The endoscope has a function of changing a shooting magnification (scaling function, zooming function) by advancing and retracting the moving lens holding barrel. Japanese Patent Application Laid-Open Publication No. 2010-243195 discloses a technique for an electrostatic encoder that is contained in the endoscope so as to measure either a position or a displacement of the moving lens.
Moreover, Japanese Patent No. 4804325 (Japanese Patent Application Laid-Open Publication No. 2008-151988) discloses a lens barrel including a lens holding member movable in an optical axis direction with respect to a fixed member, and a voice coil motor that drives the lens holding member in the optical axis direction along a guide member, and a technique of urging the lens holding member to the guide member in one direction using leakage flux from a yoke of the voice coil motor.